C#编程小技巧

1.一个应用程序只能被用户打开一次
 Process mobj_pro =Process.GetCurrentProcess();
            Process[] mobj_proList=Process.GetProcessesByName(mobj_pro.ProcessName);
            if(mobj_proList.Length>1)
            {
                MessageBox.Show("当前的应用程序已打开！", "系统提示", MessageBoxButtons.OK, MessageBoxIcon.Exclamation, MessageBoxDefaultButton.Button1);
                return;
            }
2.一个框架窗口下只打开一个子窗口
CustomerAdd pobj_CustomerAdd; 
            Form pobj_CustomerAdd_Return=CheckIsExit("CustomerAdd");
            if(pobj_CustomerAdd_Return==null)
            {
                pobj_CustomerAdd=new CustomerAdd();
                OpenSheet(pobj_CustomerAdd);
            }
            else
            {
                OpenSheet((CustomerAdd)pobj_CustomerAdd_Return);
            } 
void OpenSheet(Form pobj_form)
        {
            pobj_form.MdiParent=this;
            pobj_form.Show();
        }

        /**////

        /// 判断窗口是否存在
        ///

        /// 窗口的名称
        /// 存在返回此窗口的实例 不存在返回null
        Form CheckIsExit(string ps_windowName)
        {
            for(int i=0;i            {
                if(this.MdiChildren[i].Name==ps_windowName)
                {
                    return this.MdiChildren[i];
                }
            }
            return null;
        }
3.弹出式窗口显示渐变效果
在页面上添加一个timer控件fadeTimer,interval设为50
类的实例变量为
private m_showing=true;
在form_load中写：
Opacity = 0.0;
            Activate();
            Refresh();
            fadeTimer.Start();
            Refresh();    在timer控件的Tick事件中写：

if (m_showing)
            {
                double d = 1000.0 / fadeTimer.Interval / 100.0;
                if (Opacity + d >= 1.0)
                {
                    Opacity = 1.0;
                    fadeTimer.Stop();
                }
                else
                {
                    Opacity += d;
                }
            }
            else
            {
                double d = 1000.0 / fadeTimer.Interval / 100.0;
                if (Opacity - d <= 0.0)
                {
                    Opacity = 0.0;
                    fadeTimer.Stop();
                }
                else
                {
                    Opacity -= d;
                }
            }
4.在控件textbox中实现按回车键相当于tab键的作用
public class OSTextBox:TextBox
    {
        public OSTextBox()
        {
           
        }

        bool mb_IsKeyEnter=true;

        [
        Category("Data"),
        DefaultValue(true),
        MergableProperty(false)
        ]
        public bool IsKeyEnter
        {
            get
            {
                return mb_IsKeyEnter;
            }
            set
            {
                mb_IsKeyEnter=value;
            }
        }

        protected override void OnKeyPress(KeyPressEventArgs e)
        {
            base.OnKeyPress (e);
            if(mb_IsKeyEnter)
            {
                if (e.KeyChar == (char)Keys.Enter)
                {
                    SendKeys.Send("{Tab}");
                }
            }
        }

    }